The invention concerns a method for generating calibration signals for calibrating spatially remote signal branches of antenna systems.
In calibrating signal branches of antenna systems, the calibration signals are usually centrally generated with the corresponding frequency at which the calibration should be conducted. Here it is problematic that the distributor lines have a dispersive behavior over the frequency. That is, the signal transit times are frequency and temperature-dependent, wherein the dependency is greater the higher the absolute frequency. Moreover a signal line has varying damping as a function of frequency, temperature, bending radius of the lines, and age.
Due to imprecise adaptations to impedance, standing waves arise in connection with known methods, resulting in a wave-like amplitude behavior of the signals. A calibration is consequently made difficult.
Known calibration measuring devices are usually stationarily incorporated into the antenna system to be gauged. The disadvantages here are the large amount of space required for the measuring devices and the complicated and changing environmental conditions, for example, when installing measuring devices in the wing tips of an airplane.
A further disadvantage is that with known systems, frequency-selective filters are used, which leads to an insufficient timing accuracy due to frequency-specific group transit times. Furthermore, these group transit times are temperature and age-dependent. Nonetheless, a high level of timing accuracy is required for certain measuring methods since time differences in the arrival of received signals at the various signal branches of the antenna system are relied upon for ascertaining the direction of reception. This is also referred to as the delta time of arrival method. The direction of reception is moreover an important criterion for localizing senders.